Method of building fabric elastomeric containers and said containers



Sept. 10, 1968 K. D. ROBINSON ET AL 3,400,741

METHOD OF BUILDING FABRIC ELASTOMERIC CONTAINERS AND SAID CONTAINERSOriginal Filed April 19, 1963 INVENTOR LADISLAV A. GURSKY KEITH D.ROBINSON CHARLES A. SUTER ATTRNEY United States Patent 3,400,741 METHODOF BUILDING FABRIC ELASTOMERIC CONTAINERS AND SAID CONTAINERS Keith D.Robinson, Mogadore, Ladislav A. Gui-sky, Kent, and Charles A. Suter,Cuyahoga Falls, Ohio, assignors to The Goodyear Tire & Rubber Company,Akron, Ohio, a corporation of Ohio Continuation of application Ser. No.274,280, Apr. 19, 1963. This application Jan. 25, 1967, Ser. No. 611,773

15 Claims. (Cl. 150-1) ABSTRACT OF THE DISCLOSURE A container andmethods of forming said container by forming a body portion withsuitable fabric, coating the fabric with a liquid polyurethane reactionmixture and a barrier layer, if desired, turning the body portion insideout to expose the former inside surface, coating the surface with aliquid polyurethane reaction mixture, closing the body portion tocomplete the container and attaching fittings, the said body portionbeing displayed by external means to facilitate the coating of theoutside surface. Alternately, the closed container is inflated andcoated with the liquid polyurethane reaction mixture and a barrierlayer, if desired, from inside the container.

This application is a streamlined continuation of Ser. No. 274,280 filedApr. 19, 1963, and now abandoned.

This invention relates to a method of producing elastomeric fabriccontainers which are liquid tight to said containers. More specifically,it relates to a method of forming large fuel storage tanks.

Heretofore the building of large fabric rubber containers such asportable or temporary fuel storage tanks has required very expensivecalenders to produce the rubberized fabrics, then the rubberized fabrichad to be cut, shaped and cemented. Then the built rubberized fabrictank had to be placed in a large autoclave to be cured. Consequently theproduction cost per gallon of storage on liquid containers so producedWas very high and these temporary storage vessels offered little costadvantage over permanent construction such as metal or wooden vessels.

The object of this invention is to provide a method of makingelastomeric fabric containers more economically and to eliminate theneed for calenders and the curing equipment normally used inconventional rubber fabric construction.

Additional objects and advantages will be evident from the followingdescriptions, claims and drawings wherein FIG. 1 is a plan view of theseveral pieces of fabric assembled and stitched together with only partof the last seam 16 forming the tube completed.

FIG. 2 is a cross sectional view along 2-2 of FIG. 1.

FIG. 3 is the same view as FIG. 2 except this view shows the finishedcontainer.

FIG. 4 is a plan view of another embodiment showing several pieces offabric assembled and stitched together with only part of the seamsforming the tube completed but with the end caps being formed as anintegral part of the tube fabric.

FIG. 5 shows a rectangular shaped container which is free of seams andhas two openings for communication with the inside of the container.

FIG. 6 is a partial view of the tank showing the handle assembly.

3,400,741 Patented Sept. 10, 1968 In accordance with one embodiment ofthe present invention, the fabric is cut into strips of the desiredlength and then assembled by overlapping the edges of the fabric whichmay be of the polyamide, polyester, polynitrile, polyurethane, metal orglass fiber, cellulose or modified cellulose type fabric and stitchingto form individual seams. The several strips of fabric are then foldedover and the last seam made to form a tube. This tube is spread fiatupon a plane surface or alternately the tube can be suspended from asuitable support. Then at least one and preferably two coats of a liquidpolyurethane reaction mixture is applied to the exposed surface of thetube. Then at least one and preferably two coats of a material suitablefor forming a fuel vapor barrier is applied to the polyurethane coatingprior to the time the polyurethane reaction mixture has cured. Then ifdesired at least one and preferably two or more coats of a liquidpolyurethane reaction mixture may be applied over the vapor barrier suchas a polyamide or a polyvinyl alcohol. It should be evident that sinceonly that portion of the tube having its surface exposed can be coated,the tube should be turned over and spread fiat to expose the surfaceheretofore hidden. The newly exposed surface according to the preferredpractice then is given at least one coat of polyurethane followed by atleast one coat and preferably two of a vapor barrier material and atleast one and preferably two coats of polyurethane over the vaporbarrier in the manner heretofore described.

With the outside surface of the tube coated with polyurethane andcontaining a vapor barrier, the tube is ready to be turned inside outwhich may be accomplished by holding one end and folding the other endback over the tube to turn the tube wrong side out. With the tube turnedwrong side out, the vapor barrier will be on the inside of the finishedcontainer. Also this exposes the surface of the tube previously on theinside of the tube which has not been coated with polyurethane. Againthe tube is spread flat on a plane surface or alternately is suspendedfrom a support and at least one and preferably two or more coats ofpolyurethane is sprayed onto the exposed surface. It will be necessaryto turn the tube over and spread it flat on the surface again to exposethe hidden surface. The newly exposed surface is given at least onespray coat of a liquid polyurethane reaction mixture. Now the tube isready to have the end members put into position and attached to form aliquid type container, although by the preferred practice the endmembers are attached before coating the outside of the tank withpolyurethane.

The end members may be formed by folding a suitable piece of fabrichaving the necessary dimensions into a U shape and cementing theseU-shaped members on each end of the tube. It is a preferred practicethat both the inside and outside of the U end members be coated withpolyurethane to give at least two coats on the inside with at least oneof the inside coats of polyurethane also having a vapor barrier materialadhered thereto. The seam between the end member and the end of the tubeis best formed by applying a coat of a liquid polyurethane reactionmixture or other suitable cement within the seam and then pressing thefabric down in the overlapped area and then curing the liquid reactionmixture to obtain proper adhesion within the seam area.

Although the access openings can be made and attached in any stage ofmanufacture of the container, the preferred practice is to cut thefabric and attach the fitting after the application of the firstpolyurethane coat. The

preferred practice permits the fittings to be placed in position on thefabric and be built as an integral part of the tank to thereby obtain acontainer having additional resistance to fitting failures.

This invention may be better understood by referring to FIG. 1 whereinnumeral indicates several pieces of fabric laid'out side by side to givea pattern as shown. These individual pieces of fabric 10 have beenstitched together to form the seams 11 which are more clearly shown inFIG. 2. The numeral 12 indicates the sewed stitch. It should be notedthat the respective edges of the fabric strips 13 and 13a permit theliquid polyurethane reaction mixture to be applied between and over theoverlapped area and when the overlap area is pressed down and thepolyurethane cured the finished seam has the appearance shown in FIG. 3with the polyurethane 14 being shown between the sea-m overlaps and ontop and bottom of the sewn area by the numeral 15. Also, numeral 43indicates a polyamide vapor barrier and numeral 44 represents the topcoat of polyurethane. Referring again to FIG. 1 it will be seen thatwhen the last seam 16 is formed the fabric is formed into a tube havingopen ends 17 and 18 respectively.

FIG. 1 shows a preferred embodiment which reduces the number of seams tobe formed and also reduces the labor of building the end member. In thisembodiment some of the strips of fabric project beyond the tube ends 17and 18 respectively as shown by numerals 19 to supply fabric for formingthe end caps. After the tube has been formed and has had the insidesurface of the tube and end caps coated with polyurethane and the vaporbarrier, the end cap member 19, according to one building practice, isfolded over in the manner shown by numeral 20 to form a U. The free endof the end member 19 is cemented to the tube end 17 in the overlappedarea 21 to enclose the open end of the tube.

It has been found desirable to use a corner block 22 to form the scam inthe corner areas 23. After the end cap member 19 has been cemented inthe overlap area 21, it is preferred to trim the corner along the dottedline 31 to remove the triangular shaped fabric 32 shown in dottedoutline. Then the corner block 22 is placed inside the tank in theposition shown in FIG. 4. The corner block is preferably treated with areleasing material such as Johnsons paste wax and then the exposed waxsurface of the block and the surrounding area of the fabric in thevicinity of the corner is coated with a polyurethane liquid reactionmixture. After a suitable thickness of polyurethane is obtained a spraycoat of a suitable vapor barrier material may be applied over thepolyurethane before the polyurethane has cured. Then additional coats ofpolyurethane may be applied over the vapor barrier layer. A knit fabriccut essentially to the size and configuration shown in FIG. 4 by numeral41 is spread over the corner block and adhered to the liquidpolyurethane reaction mixture prior to the time it has set, then thecloth is pulled tight around the outer curvature 26 of the corner blockwhich has previously been coated with the necessary coats of the liquidpolyurethane reaction mixture and vapor barrier. Thus, with the clothcemented in place over the corner blocks the position of the cornerblock will be outlined by the line 24.

Once the corners have been prepared in this manner then the tank isready to be coated on the outside with the necessary coats of a liquidpolyurethane reaction mixture to give a rubberized tank. Also, it ispreferred to have the access openings and fittings 27 made and placed onthe container prior to the time the corner blocks are put in place asthis will permit the corner blocks to be removed through the accessopenings. Also, this technique permits the fabric stress ring 28 whichis held to the metal nut ring 29 by the flange 30 to be formedintegrally with the container when the outside surface of the containerand the corners are spray coated with the liquid polyurethane reaction.mi l t The handle assembly 33, where needed, is attached to the tank bypressing the assembly 33 down on the fabric while the liquidpolyurethane reaction mixture is still very fluid and maintainingpressure on the assembly until the reaction mixture has cured. Then thespray coat of liquid polyurethane reaction mixture is applied over thebody portion and the assembly to form the handle as an integral part ofthe tank. It is preferred to put a piece of cardboard coated with wax orother releasing agent under the handle 34 in the area between the slipstraps 35 to keep the handle from being stuck to the body 36 of thehandle assembly. Normally the fabric handle 34 is sewn to the fabric ofthe body 36 near the ends 37 and 38.

Reference to FIG. 5 will show a container which is free of seams. Thebody portion of this container is formed by knitting or weaving a fabricinto the required length and circumferential dimensions, then the accessopenings 25 and are cut into the fabric and the necessary fittings 27and 42 are placed on the opening. Then the outside of the fabric bodyportion is covered with at least one coat of a liquid polyurethanereaction mixture and reacted to form a set and cured polyurethaneelastomer. Then .a suitable air blower is placed in the access openingand used to inflate the container. With the containers inflated aworkman can enter the inside of the container and spray coat the insideof the container with the liquid polyurethane reaction mixture and alsoapply the polyamide vapor barriers. It should go without saying that theworkman inside the container should be equipped with a suitable gas maskor other breathing equipment. Since the liquid polyurethane reactionmixtures will normally set and cure at room temperature in a manner of afew minutes to several days depending on the nature of the polyurethanereaction mixture, there is no need to place the container in a curingoven although it may be found advantageous to subject the finishedcontainer to a temperature of about l00250 F. for a period of one toseveral hours where maximum physical properties are desired in a hurry.

A suitable polyurethane coating composition comprises a liquid reactionmixture of (1) an organic polyisocyanate and (2) a reactive hydrogencontaining polymeric material such as the polyesters, polyesterarnidesand polyethers dissolved in sufficient solvent to yield a sprayablemixture, and (3) suflicient crosslinking agent to react 'with the freepolyisocyanate. Normally, the polyurethane coating composition shouldcontain from about 40 to essentially 100% solids. Coating compositionscontaining less than 40% solids can be used, too. However, where thesolid content of the coating composition is very low the individualcoats will be thinner and the amount of the solvent to be disposed of orrecovered will be larger than with a higher solid content coatingcomposition. About and even higher solid content coating compositionsare desired so long as the solid content is not too high to preventuniform coating of the fabric or a tendency to flow. Preferably thesolid content should be about to or higher if the mixture is stillapplicable at this solid content. As indicated above the thickness ofeach spray coat is to a certain extent determined by the solid contentof the spray. Also the solid content of the spray effects the solventpollution problem in the spraying area, therefore it is desirable thatthe solid content of the spray composition be adjusted to give a spraycoat of about 5 to about 20 mils in thickness. Where the coatingthickness per spray pass exceeds about 5 to 10 mils the coating onvertical surfaces frequently exhibits a tendency to sag or flow insteadof going on as a satin-smooth film.

Any of the reactive hydrogen containing polyesters, polyesteramides andpolyethers suitable for making polyurethane castings useful as tirecompositions may be used either as is or by suitable modifications toprepare the coating polyurethane compositions of this invention. Ingeneral the polyesters are preferred over the polyethers for thepreparation of the polyurethane coating compositions. This preference isbased primarily upon the fact the polyesters produce coatings of greaterstrength and solvent resistance than the polyethers but the polyethersare preferred in the exposed surface where hydrolysis and bactericidalresistance is needed.

Representative examples of the polyesters useful in this invention arethe condensation products of a glycol with an organic dicarboxylic acidor anhydride having a molecular weight of about 700 to 5000 andpreferably from 1000 to 3000. Representative glycols are ethylene,propylene, tetramethylene, pentylene, decamethylene, etc. Representativeexamples of the organic dicarboxylic acids or anhydrides are succinic,glutaric, adipic, phthalic, terephthalic, isophthalic, suberic, sebacic,pimelic, and azelaic. Also, small amounts, i.e., l to or more, orcertain trior higher functional polyols and acids can be used to producea small amount of branching in the polymeric material and thereby varythe stiffness of the fabric obtained by spray coating. This is desirablewhere a tank is desired that will not collapse when empty.

The prepolymers of this invention may be prepared from reactive hydrogencontaining polymeric materials (hereinafter sometimes referred to in amore restricted sense as polymeric glycols or polyols) and an organicpolyisocyanate by the procedures well known to the art. Any of a widevariety of polymeric glycols having a molecular weight of from 750 to10,000 may be used. Of the polymers prepared from polyalkylene etherglycols, the polytetramethylene ether glycols are referred. Also,numeral 43 indicates a polyamide vapor barrier and numeral 44 representsthe top coat of polyurethane. It is to be understood that other polyolssuch as polyalkylenearylene ether glycols or triols, polyalkyleneether-thioether glycols or triols and polyester glycols :may be used.

In the preparation of the isocyanate-terminated polymers, a molar excessof a polymeric polyol such as a polyalkylene ether glycol or polyesterglycol is first reacted with an organic diisocyanate to prepare apolyurethane glycol which may subsequently be reacted with a molarexcess of an organic diisocyanate so as to prepare anisocyanate-terminated polymer. Alternatively, the polymeric glycol maybe reacted directly with a molar excess of an organic diisocyanate. Inthe preparation of these polymers, overall molar ratios of organicdiisocyanate to polymeric polyol of between 1.211 and 12:1 should beused at temperatures ranging from about 20 C. to about 150 C. Betterresults are obtained at ratios of about 1.5 :1 to 2.5 :1, as less timebetween spray coats is required.

Any of a wide variety of organic diisocyanates or mixtures thereofcontaining some higher functional isocyanate may be employed for thepreparation of the isocyanate-terminated polymer, including aromatic,aliphatic and cycloaliphatic diisocyanates and combinations of thesetypes. Representative compounds include toluene- 2,4-diisocyanate;mixtures of toluene-2,4- and -2,6-diisocyanates; m-phenylenediisocyanate; 4-chloro-1,3-phenylene diisocyanate; 4,4'-biphenylenediisocyanate; 1,5- naphthylene diisocyanate; 1,4-tetramethylenediisocyanate; 1,6-hexamethylene diisocyanate; 1,10-decamethylenediisocyanate; 1,4-cyclohexylene diisocyanate; 4,4-methylene-bis(cyclohexyl isocyanate) and 1,5-tetrahydronaphthylenediisocyanate. For purposes of the present invention, thetoluene-diisocyanates; diphenylmethane-4,4- diisocyanate and3,3'-dirnethyl-4,4'-bisphenylene diisocyanate are preferred, and theserespective diisocyanates are sometimes hereinafter referred to forconvenience as TDI, MDI and TODI.

These prepolyrners are dissolved or dispersed in suitable solventshereinafter described and then are mixed with a crosslinking agent whichpreferably is dissolved or dispersed in a suitable solvent. The amountof solvent used for preparing the dispersion of the prepolymer ormixtures of polymeric polyols and polyisocyanate and the crosslinkingagent are determined primarily by the viscosity desired in the mixtureand the nature of the spraying equipment in which the mixture is to beused. If high pressure spray equipment is used, the amount of solventrequired may be less as higher viscosities can be tolerated. Hence, thesolid content of the reaction mixture may be very high and contain onlya few percent solvent. Also, it should be appreciated that where thereaction mixture is essentially free of prepolymer, there is less needto usesolvent and in some cases no solvent need be used. Thecrosslinking agent may be a material containing three or more reactivegroups, e.g. glycerol or triethanolamine, but bifunctional materials arepreferred. In general, the bifunctional materials yield products havingsuperior spraying properties. Representative classes of compoundssuitable for use as crosslinking agents are the glycols, the diamineshaving primary or secondary amino groups, the dicarboxylic acids, thehydroxy amines, the hydroxycarboxylic acids and the amino-carboxylicacids. Representative examples of suitable compounds belonging to theseclasses are ethylene glycol; 1,3-propane-diol; 1,4- butane-diol;ethylene diamine; trimethyle-ne diamine; tetramethylene diamine;m-phenylene diamine; oand mdichlorobenzidine; 2,5-dichloro-phenylenediamine; 3,3- dichloro-4,4-diamine-diphenyl methane; dianisidine; 4,4-diamino-diphenyl-methane (hereinafter sometimes referred to as MDA);naphthylene diamines; toly1ene-2,4- diamine; p-aminobenzyl aniline; 0-or p-amino-diphenylamine; a-aminoethyl alcohol; 2-amino-1-naphthol;maminophenol; 2-methyl-2-amino propanol. The preferred glycolcrosslinker is butane diol.

The fast amine crosslinkers such as MDA are preferred in making pillowtanks and related sprayed liquid containers as the fast aminecrosslinkers permit the sprayed fabric container to be turned or movedwith a shorter cure time. Hence, the time between successive spray coatsis shorter and thereby permits more efiicient utilization of the sprayequipment and floor space.

By the term fast amine crosslinkers is meant those diamines whichdevelop a turbidity inside of about 10 to 30 seconds with the boilingmethylene chloride test. By this method essentially a saturated solutionof the diisocyanate and diamine are each made up in methylene chloride.This usually gives about .2 to .5 molar solution of the diisocyanate andthe diamine when dissolved in methylene chloride. The boiling methylenechloride solutions of the diamine are mixed and then time required todevelop a turbidity is measured. Those diamines which develop turbidityafter 30 seconds are considered to be slow diamines. Where the slowdiamines are used, the time required for the spray coat to becometack-free is appreciably longer than that required for the fastdiamines. Therefore, it is necessary to allow more time before the nextspray coat is applied, when using slow diamines such as methylenedichloroaniline (MOCA) or dichlorobenzidine (ODCB). Some combinationsusing the slow curing diamines are as follows:

- TODIMOCA TODIODCB TODIAPS Naphthalene diisocyanate-MOCA NaphthalenediisocyanateODCB Naphthalene diisocyanateAPS 4,4'-diphenyldiisocyanateMOCA 4,4-diphenyl diisocyanateODCB 4,4-diphenyldiisocyanateAPS APS is bis(3,3-amino phenyl) sulfone, a fast amine.

Combinations of isocyanate and fast curing diamines especially wellsuited for use in this invention are TDI-MDA MDIMDA TODI-MDA Any of thenon-reactive solvents normally used in making paints which are suitablefor spraying may be used in this invention. Representative examples ofthese are benzene, toluene, the paraffinic naphthas, the naphthenicnaphthas, the aromatic naphthas, ethyl formate, propyl formate, butylformate, amyl formate, ethyl acetate, propyl acetate, methyl acetate,butyl acetate, amyl acetate, acetone, methyl ethyl ketone, diethylketone, methyl isoamyl ketone, Cellosolve acetate, Cellosolve propylate,Cellosolve acetate butyrate, dioxane, lower boiling nitro alkanes, etc.Mixtures of certain solvents in particular amounts may be desirable toobtain satisfactory spreading properties and evaporation rates when thepolyurethane spray composition is applied to a surface. This isespecially true where very volatile solvents such as benzene and acetoneare used.

Also, it is desirable to add to the spray composition certain pigmentsand other additives such as surface active agents, leveling agents, forinstance, cellulose acetate butyrate, and other additives well known tothe spray coating art. In particular, it is desirable to add about 0.5to parts and preferably about 1 to 2 parts of a pigment on a hundredparts of prepolymer basis to improve the weather and reflectivecharacteristics.

Submicroscopic pyrogenic silica such as prepared in a hot gaseousenvironment by the vapor phase hydrolysis of silicon tetrachloride andavailable from Godfrey L. Cabot, Inc., under the trademark Cab-O-Sil isespecially useful as a leveling agent in the sprayable polyurethanecompositions when used in about 0.1 to 15 parts per 100 parts of solidsin the solution. The preferred amount is about 0.5 to about 6 parts asthe amount of solvent needed to give a sprayable viscosity is notmaterially changed. Also, this range of pyrogenic silica gives goodthixotropic properties to the resulting sprayable composition.

In order to further describe the invention several embodiments thereofare set forth with respect thereto. However, it should be understoodthat such embodiments are set forth for illustrative and not limitativepurposes. All parts are by weight unless otherwise designated.

EXAMPLE I A pillow tank 12 feet in diameter by 42 feet was made byforming a tube of a nylon fabric and coating the inside and outside witha polyurethane liquid reaction mixture with a coating of nylon vaporbarrier material applied inside the tube. The nylon vapor barrier isapplied preferably by spraying as an N-propanol solution of thepolyamide. p

The liquid polyurethane reaction mixture used in this example wasprepared from a prepolymer. This prepolymer was prepared by reacting 6moles of toluene diisocyanate with 2 moles of a polyester prepared bythe condensation of adipic acid with an excess of a mixture consistingof 80% ethylene glycol and 20% propylene glycol and 1 mole of apolyester prepared by the condensation of adipic acid with an excess ofbutane diol.

This prepolymer was used to prepare a black master batch by mixing 240parts of this prepolymer with 142 parts of carbon black, 86 parts ofCellosolve acetate and 377 parts of methyl ethyl ketone.

A cement was madenby mixing a mixture of 51 parts of a solution ofcellulose acetate butyrate in methyl ethyl ketone, 39 parts ofsubmicroscopic silica (Cab-O- Sil) with a well dispersed mixture of 389parts of Cellosolve acetate, 220 parts of methyl ethyl ketone and. 82parts of the above mentioned black masterbatch.

Component 1 of the spray mixture was formed by mixing 349 parts of theabove cement with 548 parts of the above mentioned prepolymer.

Component 2 of the spray mixture was made by mixing 199 parts of MDAwith 538 parts of methyl ethyl ketone.

Components 1 and 2 were mechanically metered in the proportions to giveabout 0.7 to 0.9 mole of MDA for each mole of excess toluenediisocyanate over that equivalent to the polyester and were mixedcontinuously and then were sprayed. The continuous metering, mixing andspraying equipment is preferred with MDA and the other fast crosslinkerssince the mixture of components 1 and 2 remains sprayable for less than10 minutes, normally.

EXAMPLE -II A cement was made consisting of parts of a 60% coloredpigment dispersed (Marine Green) in dibutyl phthalate by paint 3 rollmilling; 324 parts of Cellosolve acetate; 271 par-ts of methyl ethylketone; 58 parts of a solution of 10% of cellulose acetate butyrate inmethyl ethyl ketone, 20 parts of Modaflow, a polymeric surfaceactiveagent supplied by Monsanto Chemical Company, and 60 parts of Cab-O-Sil.

Component 1 of the spray mixture was formed by mixing 387 parts of theabove mentioned cement with 530 parts of the prepolymer of Example I.

Component 2 of the spray mixture contained 199 parts of MDA and 538parts of methyl ethyl ketone.

Components 1 and 2 were mechanically metered in the proper proportionsinto a continuous mixer and then sprayed immediately on to the surfacesof the pillo tank.

EXAMPLE III Another two-component spray recipe satisfactory for use inaccordance with the procedure of Example I is given below.

The following prepolymer were used in the formulatrlon of Component #1of the black cements of Examp e I:

Prepolymer A A reaction product of 2 mols of tolylene diisocyanate withabout 1 mol of a polyester formed by condensing an excess of ethyleneglycol with adipic acid.

Prepolymer B Same as Prepolymer A except the mol ratio used was 1.1 to1.

9 Prepolymer C Same as Prepolymer A except propylene glycol was used toproduce the polyester.

Prepolymer D Same as Prepolymer A except methylene diphenylenediisocyanate was used .instead of toluene diisocyanate.

Prepolymer -E The same as Prepolymer C except methylene diphenylenediisocyanate was used instead of toluene diisocyanate.

Prepolymer F The reaction product of 2 mols of toluene diisocyanate with1 mol of a polytetramethylene ether glycol having a molecular weight ofabout 3000. This prepolymer was preferred for the exposed polyurethanecoating as it had greater resistance to degradation.

In making rubber tanks in accordance with this invention it has beenfound to be a preferred practice to apply the polyurethane coatings tothe fabric utilizing a polyester to prepare the liquid reaction mixture,then apply the final or outside coat of polyurethane using a liquidreaction mixture prepared from prepolymer F. A tank prepared in thismanner wherein the exposed inside -and outside surface of the tank iscoated with a polyether urethane exhibits superior resistance tobactericidal and fungicidal action and other contaminating ordeleterious influences present in the soil and in the fuels beingstored.

The amount of crosslinker used should be at least 0.1 mole per mole ofreactive hydrogen containing polymeric material and normally is about0.4 to no more than about 1 mole for each mole of polyisocyanate inexcess of that equivalent to the reactive hydrogen containing polymericmaterial. It is preferred to use about 0.6 to .95 mole of diamine foreach mole of polyisocyanate in excess of that equivalent to thepolyester or polyether polyol.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in the art that various changes and modifications may 'be madetherein without departing from the spirit or scope of the invention.

What is claimed is:

1. A method of making a container which comprises forming a body portionof a suitablefabric, said body portion being suificiently incomplete topermit it being turned inside-out, applying at least one coating of aliquid polyurethane reaction mixture to the outside surface of said bodyportion, turning the body portion inside-out, and applying at least onecoating of the liquid polyurethane reaction mixture to the uncoatedsurface of the body portion, the body portion being supported by meansof an external support while said poly-urethane reaction mixture isbeing applied to it, said liquid polyurethane reaction mixturecomprising:

(a) a reactive hydrogen containing polymeric material of about 700-6000molecular weight, which is a hydroxyl terminated polyester, a polyetherpolyol, or a polyester amide,

(b) an organic polyisocyanate, and

(c) a crosslinking agent which is a diamine, a glycol or anaminoalcohol.

2. A method according to claim 1, in which, in addition to thepolyurethane, at least one coat of a vapour barrier material is appliedto at least one of said surfaces.

3. A method according to claim 2, in which the coat of vapour barriermaterial is sandwiched between successive coats of polyurethane.

10 4. A method according to claim 2 in which the vapour barrier materialis a polyamide.

5. The method of claim 1 wherein the exposed surface of the polyurethanecoating is formed from a liquid polyurethane reaction mixture containinga polyether polyol.

6. The method of claim 1 wherein the exposed surface of the polyurethanecoating is formed from a liquid polyurethane reaction mixture containinga polytetramethylene ether glycol.

7. A method of forming a container comprising the successive steps of 2(a) forming a body portion of a suitable fabric,

(b) attaching the desired access fittings to the body portion,

(c) applying at least one spray coat of a liquid polyurethane reactionmixture to at least one surface of the body portion and reacting saidmixture to form a set and cured elastomer, said liquid polyurethanereaction mixture comprising (1) a reactive hydrogen containing polymericmaterial of about 700*6000 molecular weight selected from the classconsisting of the hydroxyl terminated polyesters, the polyether polyolsand the polyester amides,

(2) an organic polyisocyanate, and

(3) a crosslinking agent selected from the class consisting of adiamide, a glycol and an aminoalcohol.

8. The method of claim 7 wherein the inside of the container has atleast one coat of a vapour barrier material adhered to the polyurethanecoating.

9. The method of claim 7 wherein the body portion is formed by attachingthe edges of at least one piece of fabric together to give the desiredconfiguration.

10. The method of claim 7 wherein a portion of the assembled fabric issufficiently longer than the other portion to permit the longer portionto be used as a cap member.

11. The method of claim 7 wherein the exposed surfaces of thepolyurethane coating is formed from a liquid polyurethane reactionmixture containing a polyether polyol.

12. The method of forming a container having at least one access openingcomprising the steps of:

(a) forming at least one piece of fabric intoa tube having the desiredlength and diameter by fastening the fabric along the edges to form aseam;

(b) applying at least one spray coat of a liquid polyurethane reactionmixture to the outside of the fabric tube;

(c) turning the tube inside out;

(d) applying at least one spray coat of a liquid polyurethane reactionmixture to the instant outside of the tube, and

(e) attaching a fabric end cap to at least one end of the tube to givean enclosed liquid-tight body, said fabric of the end cap in thefinished container having on the inside and outside surfaces at leastone spray coat of a liquid polyurethane reaction mixture.

13. A container having a fabric body portion and at least one fittingfor access to the inside of the container, said fabric of the bodyportion having each of its sides covered with at least one spray coat ofa liquid polyurethane reaction mixture which has been reacted to form aset and cured elastomer, said liquid polyurethane reaction mixturecomprising:

(a) a reactive hydrogen containing polymeric material of about 700-6000molecular weight selected from the class consisting of the hydroxylterminated polyesters, the polyether polyols and the polyester amides,

(b) an organic polyisocyanate, and

(c) a crosslinking agent selected from the class consisting of adiamide, a glycol and an amidoalcohol.

14. The container of claim 13 wherein at least one coat of a polyamidevapour barrier material is adhered to the polyurethane coating on theinside of the container. 15. The container of claim 13 wherein theexposed surfaces of the polyurethane coating is formed from a liquidpolyurethane reaction mixture containing a polyether polyol.

References Cited UNITED STATES PATENTS Kern et al 150-2 X Schofield161405 X Porteous 117161 X Hutchison et al 150-0.5 King et a1 1502Elliott.

Lein Q. 190-53 Beal 264264X Cunningham 1500.5

12 9/1955 Noland '61 al 15669 X 6/1956 Grimm ISO-0.5 6/1956 Dryg et a11501 8/1957 Freedlander 161-405 X 8/1959 Croco 117-161 X 1/ 1961Mallonee 26075 X FOREIGN PATENTS 10/ 1911 Great Britain. 11/ 1955 GreatBritain.

OTHER REFERENCES Modern Plastics Encyclopedia Issue For 1959 (September1958), vol. 36, No. 1A, p. 132, col. 2, Lines 4-8.

15 DONALD F. NORTON, Primary Examiner.

22 3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3l- 7 4- Dated September 196 8 Inventor(s)Keith D. Robinson, Charles A.Suter and Ladislav A.

Gursky It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

I'" Claim 7, line 27, "diamide" should read diamine Claim 13, line 73,"diamide" should read diamine SI'GEILU Mu SEALED BEE 2 3 19$ (SEAL)Afloat:

mmdm'nmher'k- WILLIAM E. SGHUYLER, JR. Am i Offi Commissioner of Patents

